In a known machine of this kind, and which is described in French Pat. No. 2.010.323, the tool-carrying arms of the machine are moved outwardly for tedding operations by pivoting their support bearing about a substantially horizontal axis, until a corresponding roller of the tool-carrying arm has been withdrawn from the central guide cam. To return the tool-carrying arms to the windrowing position, it is necessary to make sure that the rollers really engage the guide cam, and are not engaged above or below it, which might damage the control mechanism, when the raking wheel is rotating.
Moreover, because of the profile of the guide cam, the rollers of the tool-carrying arms can only engage with, and disengage from, one part of the cam. As this part is located in a flat zone of the cam, each roller has to be successively brought into this zone, in order to be able to withdraw from, or be engaged with the cam. This is a tedious and time-consuming operation.
Also, when passing from one operating setting to the other, the operator may forget to switch one or more of the tool-carrying arms on the same raking wheel from one operation to another. This may not only disrupt operations, but may even cause damage to the machine.
Finally, the means serving to immobilize the tool-carrying arms in relation to the raking wheel during tedding operations are located on the periphery of an upper cover of the machine, and on the tool-carrying arms in the vicinity of the operating tools. Thus the immobilizing means are exposed to dust, and can become tangled with fodder, which may impair their operative usefulness.
In the machine described in French patent application no. 2.307.458 the change of the tool-carrying arms from the windrowing setting to the tedding setting, and vice versa is mechanised. However the disengagement or re-engagement of the rollers with the cam takes place only one at a time, and solely in the flat zone of the cam. There is still a risk of an incorrect adjustment, in the event the user fails to actuate the mechanism causing the change in sufficient time. Lastly, the means to immobilize the tool-carrying arms in relation to the raking wheel during the tedding operation are also exposed to dust, and can thus become entangled with fodder.
In another machine described in German patent application no. 2.636.081, all the tool-carrying arms on the same raking wheel are changed together from the windrowing setting to the tedding setting, and vice versa. However, in this machine the rollers or the cranks will similarly only re-engage with the guide cam in the flat zone of the cam. Consequently, articulation points have to be provided between the studs or cranks and the tool-carrying arms in order to allow the tool-carrying arms to pivot relative to the cranks when the respective rollers cannot enter the guide cam directly when passing to the windrowing setting. In addition, each tool-carrying arm has to be fitted with a spring which bears on the stud or crank, so as to bring about the engagement of its roller with the guide cam on reaching the flat zone of the cam. These articulation points and springs make the machine fragile and unreliable in operation, as the rollers are not positively locked to the guide cam.
Finally, the means provided to immobilize the tool-carrying arms relative to the raking wheel during tedding are also exposed to dust and can become entangled wth fodder.